^(237)Np(V)在膨润土上的吸附行为研究

STUDY ON ADSORPTION OF ^(237)Np(Ⅴ) ON BENTONITE

以甘肃红泉膨润土为预选的缓冲、回填材料,研究了核素237Np在该材料中的吸附行为。在大气和低氧(氧含量低于5×10-6mol/mol的Ar气气氛)两种条件下,分别测定了237Np在混合型、Mg 型、Ca 型三种膨润土上的吸附分配比Kd值;并以混合型膨润土为例,研究了pH值和CO2-3浓度对Kd值的影响。得到如下主要结果:(1)大气条件下,237Np在混合型、Mg 型、Ca 型膨润土上的吸附分配比Kd分别为:47.3,52.0,42.4mL/g;低氧条件下分别为:89.3,38.8,29.0mL/g;(2)低氧条件下,混合型膨润土在最终pH<9.2时,随着pH的升高,Kd值增大,在pH=9.2时,出现最大值;(3)在大气和低氧两种条件下,在Np(V)的浓度低于NaNpO2CO3的溶解度时,随着CO2-3浓度增加Kd值减小。结果表明,混合型膨润土对Np(V)有较好的吸附能力。

The adsorption of 237Np(Ⅴ) for bentonite as buffer/backfill material is investigated.The adsorption coefficients of 237Np are determined for three kinds of bentonite under atmosphere and anoxic atmosphere. Furthermore, it is studied that how Kd values are affected by pH and CO2-3. The results shows as follows: (1)Adsorption coefficients Kd under atmosphere: mixed bentonite, 47.3 mL/g; Mgbentonite, 52.0 mL/g and Cabentonite, 42.4 mL/g.The corresponding Kd under anoxic atmosphere:89.3 mL/g,38.8 mL/g and 29.0 mL/g, respectively. (2)Under anoxic atmosphere,when pH is lower than 9.2, Kd of the mixed bentonite increases with the increase of pH and the biggest Kd value appears at pH=9.2. (3) Kd of the mixed bentonite gets lower in high carbonate concentration when the total neptunium concentration is smaller than the solubility of NaNpO2CO3.